RTLOG1, Mdend, Normx | Apple II guide

335	1F41	45	09			EOR M1
336	1F43	30	04			BMI RTS1	YES,RETURN WITH MANT1 NORMALIZED
337	1F45	A5	08			LDA X1	EXP1 ZERO?
338	1F47	D0	ED			BNE NORM1	NO, CONTINUE NORMALIZING
339	1F49	60			RTS1	RTS	RETURN
340					*
341					*
342					*	EXP/MANT2-EXP/MANT1 RESULT IN EXP/MANT1
343					*
344	1F4A	20	8F	1F	FSUB	JSR FCOMPL	CMPL MANT1 CLEARS CARRY UNLESS ZERO
345	1F4D	20	5D	1F	SWPALG	JSR ALGNSW	RIGHT SHIFT MANT1 OR SWAP WITH MANT2 ON CARRY
346					*
347					*	ADD EXP/MANT1	AND EXP/MANT2 RESULT IN EXP/MANT1
348					*
349	1F50	A5	04		FADD	LDA X2
350	1F52	C5	08			CMP X1	COMPARE EXP1 WITH EXP2
351	1F54	D0	F7			BNE SWPALG	IF UNEQUAL, SWAP ADDENDS OR ALIGN MANTISSAS
352	1F56	20	00	1F		JSR ADD	ADD ALIGNED MANTISSAS
353	1F59	50	E3		ADDEND	BVC NORM	NO OVERFLOW, NORMALIZE RESULTS
354	1F5B	70	05			BVS RTLOG	OV: SHIFT MANT1 RIGHT. NOTE CARRY IS CORRECT
SIGN
355	1F5D	90	BD		ALGNSW	BCC SWAP	SWAP IF CARRY CLEAR, ELSE SHIFT RIGHT ARITH.
356	1F5F	A5	09		RTAR	LDA M1	SIGN OF MANT1 INTO CARRY FOR
357	1F61	0A				ASL	RIGHT ARITH SHIFT
358	1F62	E6	08		RTLOG	INC X1	INCR EXP1 TO COMPENSATE FOR RT SHIFT
359	1F64	F0	7E			BEQ OVFL	EXP1 OUT OF RANGE.
360	1F66	A2	FA		RTLOG1	LDX =$FA	INDEX FOR 6 BYTE RIGHT SHIFT
361	1F68	A9	80		ROR1	LDA =$80
362	1F6A	B0	01			BCS ROR2
363	1F6C	0A				ASL
364	1F6D	56	0F		ROR2	LSR E+3,X	SIMULATE ROR E+3,X
365	1F6F	15	0F			ORA E+3,X
366	1F71	95	0F			STA E+3,X
367	1F73	E8				INX	NEXT BYTE OF SHIFT
368	1F74	D0	F2			BNE ROR1	LOOP UNTIL DONE
369	1F76	60				RTS	RETURN
370					*
371					*
372					*	EXP/MANT1 X EXP/MANT2 RESULT IN EXP/MANT1
373					*
374	1F77	20	0D	1F	FMUL	JSR MD1	ABS. VAL OF MANT1, MANT2
375	1F7A	65	08			ADC X1	ADD EXP1 TO EXP2 FOR PRODUCT EXPONENT
376	1F7C	20	CD 1F			JSR MD2	CHECK PRODUCT EXP AND PREPARE FOR MUL
377	1F7F	18				CLC	CLEAR CARRY
378	1F80	20	66	1F	MUL1	JSR RTLOG1	MANT1 AND E RIGHT.(PRODUCT AND MPLIER)
379	1F83	90	03			BCC MUL2	IF CARRY CLEAR, SKIP PARTIAL PRODUCT
380	1F85	20	00	1F		JSR ADD	ADD MULTIPLICAN TO PRODUCT
381	1F88	88			MUL2	DEY	NEXT MUL ITERATION
382	1F89	10	F5			BPL MUL1	LOOP UNTIL DONE
383	1F8B	46	03		MDEND	LSR SIGN	TEST SIGN (EVEN/ODD)
384	1F8D	90	AF		NORMX	BCC NORM	IF EXEN, NORMALIZE PRODUCT, ELSE COMPLEMENT
385	1F8F	38			FCOMPL SEC		SET CARRY FOR SUBTRACT
386	1F90	A2	03			LDX =$03	INDEX FOR 3 BYTE SUBTRACTION
387	1F92	A9	00		COMPL1	LDA =$00	CLEAR A
388	1F94	F5	08			SBC X1,X	SUBTRACT BYTE OF EXP1
389	1F96	95	08			STA X1,X	RESTORE IT
390	1F98	CA				DEX	NEXT MORE SIGNIFICANT BYTE
391	1F99	D0	F7			BNE COMPL1	LOOP UNTIL DONE
392	1F9B	F0	BC			BEQ ADDEND	NORMALIZE (OR SHIFT RIGHT IF OVERFLOW)
393					*
394					*
395					*	EXP/MANT2 / EXP/MANT1 RESULT IN EXP/MANT1

II specifications

The Apple II, launched in April 1977, was one of the first highly successful mass-produced microcomputer products. It marked a significant leap in personal computing, setting standards for future developments in the industry. Created by Steve Wozniak and Steve Jobs, the Apple II differentiated itself with its user-friendly design, appealing aesthetics, and robust capabilities.

One of the standout features of the Apple II was its open architecture, which allowed users to expand and enhance the computer's functionality. This design enabled hundreds of third-party hardware and software developers to contribute to its ecosystem, resulting in an array of peripherals, including printers, modems, and storage devices. The Apple II utilized a MOS Technology 6502 microprocessor running at a clock speed of 1 MHz. Initially equipped with 4 KB of RAM, the machine could be expanded to 48 KB, accommodating more complex applications and programs.

The Apple II was also notable for its colorful graphics. It was one of the first computers to support color display, offering a 6-color palette with a resolution of 280x192 pixels in 16 colors when using its Color Graphics Card. This feature significantly enhanced the visual appeal of games and educational software developed for the platform, making computing more accessible and entertaining for various audiences.

Apple's commitment to user experience was evident in the design of the machine. It featured an integrated keyboard and a plastic case, which was both durable and visually appealing. The self-contained design included drive bays for floppy disk drives, allowing for quicker data access than traditional tape drives. It also supported audio output, enabling sound effects and music, a novelty at the time.

The introduction of the Apple DOS operating system further underscored the machine's capabilities. DOS streamlined file management and made it easier for users to navigate and manage their data. The combination of hardware and software positioned the Apple II as an educational tool and a gaming platform, fostering a vibrant software ecosystem.

The Apple II family continued to evolve, with variations like the Apple II+, IIe, and IIgs being introduced over the years. These iterations brought enhancements in memory, processing power, and graphics capabilities. The legacy of the Apple II endures, not only as a foundational product in personal computing but also as a symbol of innovation that paved the way for future advancements in technology. Its impact is still felt today, as it inspired countless developers and shaped the trajectory of the computer industry.

RTLOG1

MDEND

NORMX

II specifications